Treatment of hydrocarbon oils



June 4, 1935. w. M. STRATFORD 2,003,776

J TREATMENT OF HYDROCARBON OILS Filed Feb. 12, 1951 STILL INVENTOR BYArrwzfdw Patented June 4, 1935 TREATMENT OF HYDROCABBON OILS William M.Stratford, New York, N. Y., assignor to The Texas Company, New York, N.Y.,a corporation of Delaware Application February 12, 1931, Serial No.515,189

12 Claims.

,This invention relates to the treatment of hydrocarbon oils and hasparticular reference to the conversion of higher boiling hydrocarbonoils intdi-lower boiling hydrocarbon oils.

The invention contemplates a process involving the distillation of freshcharging stock in contact with hqt-rgapors from a cracking still, theformation of a condensate from the vapors thus evolved and theutilization of this condensate as a clean cracking stock. The process isparticularly adapted'for utilizing crude petroleum or residues thereofsince it provides forthe production of a condensate obtained from thecrude orresidue as a result of heat exchange with the hot vapors from acracking still which condensate is freed of residual oil and may thus beused as a cracking stock without the danger of excessive coke formation.

In my co+pending application, Serial No. 273,885,, there is described amethod in which a charging stock such as crude petroleum is subjected todistillation by contact with the hot vapors from a pressure or so-calledliquid phase cracking operation. The resultant residue is drawn off andthe vapors, comprising the vaporized charging stock commingled with thecracked vapors received from the cracking still, are subjected todephlegmation to thereby form a vapor fraction (from which a distillateis obtained that constitutes the desired gasoline or naphtha) and areflux condensate consisting essentially of intermediate constituentsfrom the crude charging stock combined with constituents obtained fromthe cracked vapors which are of higher boiling point than desired forthe final naphtha or gasoline distillate,'and this reflux condensate isintroduced as charging stock to the cracking still.

In the present invention the fresh charging stock is subjected todistillation by contact with hot vapors from a vapor phase crackingopera- .tion. The resultant residue is withdrawn from the system and thevapors dephlegmated to form a vapor fraction and a reflux condensate, dconsisting essentially of the higher boiling products of the vapors fromthe vapor phase cracking operation and the bulk of the heavierconstituents vaporized from the fresh charging stock, and this refluxcondensate is introduced as a charging stock to a pressure or liquidphase cracking operation. The lower boiling products from the liquidphase cracking operation are vaporized .and the unvaporized residuewithdrawn from-the system. The vapors are subjected to dephlegmation toform a vapor fraction and a reflux condensate, which may be used eitheras a charge to the vapor phase cracking operation or as acycle' stockfor recharging to the liquid phase cracking operation.

erably carried out under considerable superstmospheric pressure andlikewise the resultant vapors are dephlegmated under high pressure. Thevapor phase cracking operation is preferm ably carried out under lowersuperatmospheric pressure. preferably near atmospheric pressure. Thefractionation of the vapors from the vapor phase cracking operation iscarried out in a fractionating tower likewise maintained under 15 lowpressure. The low boiling products from the low pressure fractionatingtower of the vapor phase cracking operation are preferably returned tothe high pressure tower of the liquid phase cracking system where theyare combined with the vaporstherein and subjected to fractionation. Thisreturn of the cracked products may be conveniently done by condensingthe condensible vapors from the low pressure tower, u separating theincondensible gases and, then, pumping the condensate to the highpressure tower. If desired, however. all the vapors be returned directlyto the tower without'condensation. '0

In the preferred form of operation the reflux condensate in the highpressure tower is separated into a lower and a higher boiling'fraction.The lower boiling fraction may be taken off as a side stream from thehigh pressure a tower. and used as a charge for the vapor phase crackingoperation. The higher boiling fraction is taken from the bottom of: thesame tower and may be used as a. cycle stock for rechar ing to theliquid phase cracking 0 operation. I I

In one method of operation the reflux condensate may be withdrawn as asingle fraction from the bottom of the high pressure tower. This singlefraction may then be named entirely or in' part to either the vaporphase cracking operation or the liquid phase crack ing operation. I

In order to more fully disclose the invention reference will now be hadto the accompanying w drawing which illustrates the preferred em;-bodiment of the invention.

In the apparatus a high temperature heating coil l is connected. by atransfer line! to a cracking still 3. The heating coil is located in Theliquid phase cracking operation is prefthe high pressure tower II afurnace 4 having a burner or heating means 5. The still 3 may beinsulated so that the body of oil therein may be maintained at thedesired cracking temperature by means of the highly heated oil deliveredfrom the coil I by the transfer line 2 or, if desired, the still may bemounted in a furnace in order that the proper temperature may bemaintained therein.

A vapor line I0 serves to conduct vapors from the cracking still 3 to ahigh pressure fractionating tower or dephlegmator II. Baffles I2 areindicated'in the tower II for the purpose of insuring adequate contactof the vapors with the liquids passing therethrough. A vapor line I3serves to conduct vapors from the fractionating tower II to a condenserI4. A line I5 conducts the products from the condenser I4 to a receiverI6, .the latter having a gas release pipe I! and a liquid draw-off lineI8. A line 20 leading from the bottom of the high pres- "sure tower IIconducts reflux condensates to a pump 2]. The pump 2I then forces thecondensates through line 22 to the heating coil I. A portion of thecondensates, if desired, may be by-passed through the by-pass line 23 tothe accumulator tank 25.

' In the preferred method of operation the condensates collecting in thehigh pressure tower I I are separated into a higher boiling fraction andinto a lower boiling fraction. The lower boiling fraction maybecollected at an intermediate point in the tower and withdrawn as a sidestream through the line 24 to the accumulator tank 25.

"The accumulator tank 25 may also be provided with an inlet line inorder that an extraneous oil may be charged thereto to be used as acharging stock when all the condensates collected in the high pressuretower II are recycled to the heating coil I throughline 20, or when onlya portion of the condensates from are bypassed through the line 23, inwhich case the condensates may be insufficient to maintain the desiredvolumein the accumulator tank 25.

The liquid from the accumulator tank 25 which may be, as indicatedheretofore, an extraneous oil introduced through the line 30,

. in'g coil 32 is located within a furnace 36 which may receive heatfrom a burner 3! or other heating means. The low pressure tower isprovided with bafIle plates 38 to insure adequate contact between thevapors and the liq uids therein.

In the preferred manner of practicing the invention the fresh chargingstock, such as crude petroleum or a residuum thereof, is withdrawn bythe pump 40 from a charge tank 4| and is passed, through the line 42 andsuitable connection, either directly to the low pressure tower 35 whereit comes in contact with the hot vapors, or first mixed with the crackedproducts from the vapor phase heating coil and the mixture thenintroduced into the tower. A connection 43 may be used to pass the freshcharging stock directly to an intermediate point in the low pressuretower 35 by suitable regulation of the valve 44. A connection 45 may beused to pass the fresh charging stock in contact with the vapor phasecracked products prior to entrance to the low pressure'tower by suitableregulation of the valve 46. In either method of operation the crackedproducts from the heating coil 32 and the fresh charge are intimatelycontacted and the lower boiling constituents from the crude oil arevaporized and combined with the vapors from the vapor phase crackingoperation to be fractionated in the fractionating tower 35.

A vapor line conducts vapors from the low pressure tower to a condenser5|. A line 52 conducts the products from the condenser 5| to a receiver53 which is equipped with the usual gas release line 54 and a liquiddraw-off line 55. A pump 56 serves to withdraw the liquid from thereceiver 53 and may conduct any or all of it to the high pressurefractionating tower by way of the line 51.

The reflux condensates collecting in the low pressure tower consistingof the higher boiling constituents of the vapor phase cracked productsand the vaporized constituents of the fresh charging stock are withdrawnfrom the low pressure tower through the line 60 to an accumulator tank6|. A line 52 serves to supply an extraneous oil to the accumulator tank6| if desired. The liquids in the accumulator tank BI may be withdrawnthrough a line to a pump 66. The pump 66 then forces these liquidsthrough the line 61 to the heating coil I of the liquid phase crackingsystem.

The unvaporizedliquids or tar collectingin the lower pressure tower 35may be withdrawn from the bottom thereof through the tar line 68 andsent to storage or otherwise disposed of along with the residue from thestill 3 which likewise is withdrawn from the bottom thereof through theresidue line 69.

In practicing the invention the cracking operation in the heating coil Iand still 3 is preferably carried out in substantially the liquid phase.The cracking system may be any of the common or preferred types in whichthe temperatures andpressures are well known. I prefer, however, tomaintain a body of oil in the still 3 and to maintain the still at atemperature of approximately 750 to 900 F. therein under pressures of,for example, 100 to 500 pounds per square inch. The oil is delivered tothe still 3 from the coil I at temperatures of about 750 to 900 F. andit is ordinarily preferable to maintain the coil I and still 3 atsubstantially the same pressure, there being only the differencesinvolved in the frictional drop due to forcing the oil through' theheating coil. In some cases, however, a pressure .-reducing valve may beemployed in the transfer line 2 so that the pressure in the still 3 andtower II may be dropped a predetermined amount. The fractionating towerI I, however, is always maintained under a substantial superatmosphericpressure. In'this way the fractionation of the vapors in the highpressure fractionating tower II is carried out under a pressuresufliciently high to produce sufficient fractionation and at the sametime efiect a polymerization'or stabilization of the unstableconstituents of the vapors therein."

The vapors withdrawn through the line I3 are gasoline preferably with a-maximum boiling point in the neighborhood of 400 F. The gasolineproduced by the condensation of these vapors, as will be observed,consists not only of liquid phase cracked products but also vapor phasecracked constituents whereby a gasoline of high anti-knock quality isobtained.

In the preferred method of operation the lower boiling fraction of thereflux condensates is withdrawn as a side stream through the line 24 andaccumulated in the tank 25 for a charging stock to the vapor phasecracking system. It is to be understood, however, that other'types ofcharging stock may be used in the vapor phase cracker such, for example,as an extraneous oil supplied through the line or a portion or all ofthe combined condensates received through the by-pass line 23. In case alower boiling fraction is taken off as a side stream through the line24, the heavier fraction of the reflux condensate is preferablyconducted to the liquid phase cracking coil I where it may be introducedat an intermediate point in the coil as indicated in the drawing.

The vapor phase heating coil 32 is preferably maintained under a lowpressure in the neighborhood of atmospheric pressure. The type of vaporphase cracker and the operating conditions may vary depending on thetype of cracking system and the nature of the charging stock. Thetemperature, however, will ordinarily be maintained at approximately 900to 1050 F.

The cracked products from the vapor phase heating coil are suddenlycooled by contact with the fresh charging stock from the tank 4|.

In this way the charging stock is heated and a substantial amountthereof vaporized. The average temperature of the oil maintained in thebottom of the low pressure tower may be in the neighborhood of 600 F.The liquid drawn off from the low pressure tower through the line 68 maybe termed fuel oil. It consists essentially of the unvaporized portionof the fresh charging stock although there may be minor .amounts of thehigher boiling constituents of the vapor phase-products.

The reflux condensates from the low pressure tower consisting of a cleanall of intermediate boiling point, such as gas oil, is withdrawn throughthe line 60 to an accumulator tank where a body of clean oil ismaintained for a charging stock to the heating coil I of the. liquidphase cracking operation. If desired, an extraneous clean oil, such asgas oil, maybe supplied to the accumulator tank through the line Thevapors passing from the low pressure tower 35 consist essentially of allthe gasoline constituents from the vapor phase products together with asmall fraction of heavy boiling omitted and the vapors passed directlyto the.

high pressure tower without intervening condensation.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may

be made without departure from the spirit and scope thereof, andtherefore only such limitations should be imposed as are indicated inthe appended claims.

I claim:

1. The process of treating hydrocarbon oils that comprises subjectinghydrocarbon oil in a first cracking zone to a substantially liquid phasecracking temperature to effect conversion of the high boilinghydrocarbon oils into lower boiling hydrocarbon oils, vaporizing thelower boiling hydrocarbons of the cracked products, withdrawing theunvaporized oil from the system, fractionating the evolved vapors in afirst fractionating zone to form a gasoline-like vapor fraction, alighter reflux condensate and a heavier reflux condensate, returning theheavier condensate to said liquid phase cracking operation, subjectingsaid lighter condensate to a vapor phase cracking temperature in asecond cracking zone, contacting relatively heavy fresh charging stockwith the resulting vapors from the vapor phase cracking operation tothereby vaporize a portion of the fresh charging stock, withdrawing theunvaporized portion of the "charging stock from the system,dephlegmating the combined vapors from. the vapor phase crackingoperation and the vapors from the fresh charging stock in a. secondfractionating zone to produce a vapor fraction suitable for theproduction of gasoline and a reflux condensate suitable as a cleancracking stock and charging said clean cracking stock to the liquidphase cracking operation.

2. The process of treating hydrocarbon oil that comprises subjectinghydrocarbon oil in a first cracking zone to a substantially liquid phasecracking temperature, under relatively high pressure, to effectconversion of higher boiling hydrocarbons into lower boilinghydrocarbons, separating the resulting cracked products into vapors andliquid residue, withdrawing said residue from the process, passingvapors so obtained to a fractionating zone and therein fractionating thevapors into a lighter fraction containing gasoline hydrocarbons and aheavier fraction suitable for vapor phase cracking, removing saidlighter fraction as desired product, subjecting said heavier fractionsuitable for vapor phase cracking to a vapor phase cracking temperaturein a second cracking zone, under relatively low pressure, to effectconversion thereof into lower boiling products, contacting freshrelatively heavy charging stock comprising crude oil constituents, withthe resulting vapors from the vapor phase cracking operation, in aseparating zone, to thereby vaporize, a substantial portion of thecharging stock, isolating from the process the unvaporized portion ofsaid charging stock, passing the vapors from the vapor phase crackingoperation and the vapors from said charging stock to a secondfractionating zone and therein fractionating these vapors into a lighterfraction suitable for the production of gasoline and a heavier fractionsuitable for liquid phase cracking, and charging said last mentionedheavier fraction to said flrst cracking zone.

3. The process of treating hydrocarbon oils which comprises mixingrelatively heavy fresh charging stock, comprising residual crudeconstituents, with the hot products from a relatively low pressure vaporphase cracking operation, separating the resulting mixture into vaporsand residual liquid, in a separating'zone, removing said residual liquidfrom the process, passing said vapors to a first fractionating zone andtherein dephlegmating them to form a vapor fraction containing lighterhydrocarbons and a liquid condensate fraction containing heavierhydrocarbons suitable as a clean cracking stock, subjecting said cleancracking stock, free from said residual liquid, to conversion conditionsof temperature and relatively high superatmospheric pressure, in a firstcracking zone, to effect conversion of the high boiling hydrocarbonssubstantially in the liquid phase into lower boiling hydrocarbons,passing the resulting cracked products to a second separating zone andtherein separating the lower boiling hydrocarbons as vapors, removingremaining unvaporized products from the process, fractionating saidvapors in a second fractionating zone into a fraction containinggasoline-like hydrocarbons and a heavier fraction suitable for crackingin the vapor phase, removing said fraction containing gasoline-likehydrocarbons, as a desired product, and charging said heavy fraction tosaid vapor phase cracking operation.

4. The process of treating hydrocarbon oils that comprises subjecting aheavy hydrocarbon oil in a liquid phase cracking zone to crackingtemperature, under relatively high pressure, to effect conversion ofhigher boiling hydrocarbons substantially in the liquid phase into lowerboiling hydrocarbons, separating the lower boiling hydrocarbons asvapors, and removing the higher boiling unvaporized hydrocarbons fromthe process, simultaneously subjecting a light hydrocarbon oil in avapor phase cracking zone to cracking temperatures, under relatively lowpressure, to effect conversion thereof substantially in the vapor phase,contacting relatively heavy fresh charging stock comprising residualcrude constituents, with the resulting vapor phase cracked products, ina separating zone, to vaporize a. substantial portion of the freshcharging stock, separating the vaporized portion of the fresh chargingstock and the products resulting from the vapor phase cracking operationinto vapors and a liquid residue, removing said liquid residue from theprocess, passing said vapors to a first fractionating zone and thereinseparating them into a lighter fraction containing gasoline-likehydrocarbons and a heavier condensate fraction suitable for a cleancracking stock, charging said clean cracking stock to said liquid phasecracking zone uncontaminated by unvaporized' portions of said chargingstock, combining said lighter fraction with said vapors separated fromthe oil undergoing liquid phase cracking and fractionating the resultingmixture, in a second fractionating zone, under higher pressure than thatof said vapor phase cracking zone, to form a desired stabilized gasolinedistillate and reflux condensate of higher boiling point.

5. A process in accordance with claim 4 wherein reflux condensate fromsaid second fractionating zone is utilized as a source of said lighthydrocarbon oil subjected to vapor phase crackmg.

6. The process of treating hydrocarbon oil which comprises heating cleancharging stock to a cracking temperature in the vapor phase to produceconversion thereof into lighter products, introducing the resultingcracked products into a separating zone wherein separation of vaporsfrom liquid occurs, introducing fresh relatively heavy charging stock,comprising residual crude oil constituents, into said zone, separatelyremoving from said zone light fractions in vapor form, an intermediatecondensate free from unvaporized portions of said heavy charging stockand a heavy residue, removing said residue from the process, condensingsaid light fractions as a desired product, cracking said condensate,separating from the resulting cracked products a liquid residue and aclean condensate stock, utilizing the clean condensate stock so obtainedas said charging stock first mentioned, and withdrawing said liquidresidue from the process.

'7. A process according to claim 6 wherein said fresh relatively heavycharging stock is combined with the vapor phase cracked products priorto their introduction into said separating zone, in quantitiessuflicient to reduce the temperature of said cracked products below anactive cracking value.

8. In the conversion of higher boiling hydrocarbon oils into lowerboiling oils, the process that comprises subjecting a hydrocarbon oil ina cracking zone to cracking temperature under superatmospheric, pressureto effect cracking and vaporization; subjecting evolved vapors tofractionation in a fractionating zone while under a superatmosphericpressure in the neighborhood of 500 pounds per square inch, to form areflux condensate and a vapor fraction comprising gasoline, removingsaid reflux condensate and heating it in a separate cracking zone to avapor phase cracking temperature under a pressure approximatingatmospheric to subject the oil to vapor phase cracking, fractionatingthe products of the vapor phase cracking to separate out a heavierfraction thereof and a lighter fraction thereof comprising gasoline,introducing said lighter fraction into the high pressure fractionatingzone to thereby subject said fraction to reconditioning andrefractionation under the high pressure therein, and condensing thevapor fraction from the high pressure fractionating zone to form a finalgasoline distillate.

9. The process of treating hydrocarbon oil which comprises heating cleanrelatively heavy oil to a cracking temperature under relatively highpressure, separating the resulting cracked products into vapors andliquid residue, passing said vapors to a relatively high pressurefractionating zone, and therein separating heavier fractions ascondensate from lighter products as vapors, removing and condensing thefractionated vapors as a desired product, removing condensate formed inthe fractionating zone and passing it in a stream of restricted crosssectional area through a heating zone under relatively low pressurewherein it is heated to a cracking temperature and subjected toconversion in the vapor phase, mixing fresh relatively heavy chargingstock with the resulting cracked products immediately upon theiremergence from the heating zone, in such quantities that the temperatureof the resulting mixture is below an active cracking value, passing theresulting low temperature mixture into a separating zone wherein vaporsseparate from liquid residue, passing resulting vapors through afractionating zone wherein condensation of the heavier constituentsthereof occurs, removing resulting condensate, free from residualconstituents of the fresh relatively heavy charging stock and utilizingit as said clean charging stock first mentioned. removing fractionatedvapors from said fractionating zone second mentioned, condensing themandzintroducing the resulting condensate into the iractionating zonefirst mentioned whereby they are subjected to redistillation andbeneficial polymerization under a pressure higher than that of theirformation.

10. A process in accordance with claim 9 wherein additional refluxcondensate formed in said fractionating zone first mentioned is recycledthrough said heating zone first mentioned.

11. The process-of treating hydrocarbon oil which comprises passingfresh relatively heavy charging stock through a cracking zone wherein itisraised to a temperature in the range of 750 to 900 F. under-relativelyhigh pressure and is subjected to conversion, separating the resultingcracked products into vapors and a liquid residue, passing said vaporsthrough a fractionating zone wherein heavier constituents thereofarecondensed as reflux condensate,

- removing resulting fractionated vapors' and condensing them as adesired product, removing resulting reflux condensate from said fractionating zone and passing it in a stream of restricted cross sectional areathrough a heating zone wherein it is raised to a cracking temperature ofat'least 1000 pressure, directly admixing crude oil charging still in astream of restricted cross sectional area the amount of crude oilcharging stock so admixed being sumcient to reduce the temperature ofthe mixture below an active cracking value, passing the low temperaturemixture so obtained into a, separating zone wherein vapors separate fromliquid residue, passing resulting vapors through a second fractionatingzone wherein partial fractionation thereof takes place with theformation of a reflux condensate, removing the fractionated vapors fromsaid second fractionating zone, said vapors compris- F., underrelatively low the resulting cracked products while '5 ing gasolineconstituents, c'ondensingithe vapors so removed and introducingresulting condensate into said fractionating zone first mentioned forredistillation under higher pressure, whereby beneficial polymerizationand stabilization thereof occurs.

12. The process of treating hydrocarbon oil.

which comprises passing-fresh relatively heavy clean charging stock in astream of restricted cross sectional area through a heating zon'ewherein it is raised-to a crackingQtemp'erature, of at least 1000 F.under relatively low pressure, admixing with the resulting crackedproducts, while still in a stream of restricted cross sectional areacrude oil charging stock inquantities sufiicient to reduce thetemperature of the mixture below an active cracking value, passing thelow temperature mixture so obtained into a separating zone whereinvapors separate from liquid residue, passing resulting vapors through afractionating zone wherein heavier constituents thereof are condensed asreflux condensate, removing resulting fractionated vapors, comprisinglight; gasoline constituents, from said ffactionating zone andcondensing them, passing condensate so formed into a .secondfractionating zone wherein fractionation thereof 00- I curs underpressure considerably higher than that in said first'fractionating zone,removing reflux condensate formed in said second fractionating zone andpassing it through a separate cracking zone wherein itis raised to acracking temperature in the range of 750 to 900 E, un'der relativelyhigh pressure and conversion thereof occurs, separating the resultingcracked products into vapors and a liquid residue, passing said vaporsinto said fractionating zone 'sec-.--

0nd mentioned, and removing fractionated vapors from said secondmentioned fractionating zone andcondensing them as a desired gasolinedistillate.

WHLIAM M. STRATFORD.

.DISGLAIMEIR 2,003,776..William' ltl. Stratfcrd, New York, N. Y.TREATMENT or HYDRbChRBON OILs. Patent dated June- 4, 1935. 'Disclaimerfiled' May 20,1937, bythe assignee, The Texas Company. a

Hereby enters this disclaimer to the subject matter of claim 1thereof,except as said claim a plies to-a process in which therelativelyheavy fresh charging stock which is contacts with theresulting vaporsfrom the vapor hase cracking 0 eration 1s a relativelyheavj stock; with respect to stocks employe for conversion mto gasohneby cracking, and contains unvaporizable constituents which'are notvaporized under the conditlons of said contacting with the resultingvapors from the 'vapor phase cracking operation, and in which theresultant unvaporized portion of the charging stock is withdrawn fromthe system. y

[Ojimal Gazette Jun .15, 1937.]

